I'm having trouble with a circuit I'm putting together. I think this is how to represent it (may be wrong about that).

I'm using a SPDT switch to turn off a circuit, but I want it to turn off after a delay. I have a 12v Delay Switch Ne555 Module that I switch on when MAG is in an NC state. This works.

The issue is the circuit is permanently on and never switches off. It seems like the timer fires immediately but never switches. The module makes a buzzing noise.

If I move the timer switch to the opposite leg the timer works - it turns off immediately and then turns on after a delay - the opposite of what I want. No noise is made.


simulate this circuit – Schematic created using CircuitLab

I think the diagram is slightly wrong - there isn't two switches inside the module. I just wasn't sure how to represent a timer switch that needed voltage.

What am I doing wrong?

  • \$\begingroup\$ A few problems here, Luke. (1) You've posted to a product listing. That link will die so you need some details in the post to keep it relevant for future readers. (2) We need a datasheet with schematic diagram and specifications. There is none. The mantra here is, "No datasheet? No sale!" (3) It's a delay-on timer. You're looking for a delay off. You'll need more components to make it work. (4) It doesn't switch but it buzzes. Yes, it's a 12 V module and you're only giving it 6 V, according to your schematic. I can't figure out how you got it to work at all. \$\endgroup\$
    – Transistor
    Sep 29, 2017 at 23:00
  • \$\begingroup\$ It doesn't buzz when I use it as delay on. Seems to function with 6v fine. I thought was on or off because it has NO+NC+Common. I can't seem to find a delay off module. \$\endgroup\$
    – Luke
    Sep 29, 2017 at 23:26
  • \$\begingroup\$ You looking to build? Or just to buy something? \$\endgroup\$
    – jonk
    Sep 30, 2017 at 5:16
  • \$\begingroup\$ @Transistor's answer is correct it did work. The relay I got won't switch at 6v though. Voltage actually ranges from 5.8 to 6.2 depending on the state of the IR sensor. Looking for one that will, or the simplest solution. I could build one, but I would prefer not to. \$\endgroup\$
    – Luke
    Sep 30, 2017 at 8:17

1 Answer 1



simulate this circuit – Schematic created using CircuitLab

Figure 1. Using a delay-on timer to switch off a load after a delay.

How it works:

  • Initial conditions: SW1 is open. The time delay module NC (normally closed contact) is closed and the load is powered.
  • SW1 (an SPST will do) is closed.
  • The timer module starts timing.
  • At the end of the preset time the relay energises and disconnects the load.
  • When SW1 is opened the relay immediately resets and the load is energised again.

This circuit will do what you require if you can tolerate the switch being left in the "on" position to switch the circuit off! (It's just a matter of labeling it backwards.)

  • \$\begingroup\$ I think this works - I think my remaining problem is 6v is not enough to switch it over. I have constant power thru common on the relay, load on NO on the relay. Then I have SW1 providing the power when on. When I engage SW1 the relay gets power, a red led appears, then moments later a blue led. Problem is it won't switch off NO to NC. \$\endgroup\$
    – Luke
    Sep 30, 2017 at 1:07
  • \$\begingroup\$ Yeah, I'm almost certain the voltage is too low for that module. The source is 6.2v, but when the IR sensor is engaged drops to 5.8v. The buzzing is louder at 5.8v then 6.2v but still present. I can't seem to find any 6-7v modules though. Just 5v and 12v. \$\endgroup\$
    – Luke
    Sep 30, 2017 at 1:51

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